The exemplary embodiments relate to an ambipolar thin film transistor device, and methods for producing ambipolar thin film transistor devices.
Thin film transistors (TFTs), composed of a substrate, a gate, source, and drain electrodes, a gate dielectric layer, and a semiconductor layer, are the key elements of integrated circuits (ICs). TFT fabrication using solution processes such as spin-coating, stencil/screen printing, stamping, and jet-printing, present a low-cost manufacturing alternative to conventional photolithography. In recent decades, development of solution-processed transistors, including organic thin film transistors (OTFTs), have made significant progress. There is ample evidence that they will replace traditional crystalline or amorphous silicon technology at least in certain low-cost, and or low-end applications.
Digital circuits are largely based on complimentary metal oxide semiconductor (CMOS) structures that use both p-type and n-type unipolar transistors. The advantages of CMOS circuits are lower power dissipation, greater speed, improved immunity to noise effects, and greater tolerance of variability and shifts in transistor operating characteristics. These CMOS circuits may be constructed using unipolar transistors with either p-type or n-type semiconductor.
An example of an unipolar transistor 29 is shown in FIGS. 1A and 1B. The unipolar transistor 29 includes a first terminal 4, a second terminal 5, a substrate 6, a gate electrode 7, a dielectric layer 8 and a semiconductor layer 10. The first terminal 4 may be a source electrode, while the second terminal 5 may be a drain electrode. The semiconductor layer 10 may only be either a p-type or n-type semiconductor.
In order to design more efficient circuits based on solution process transistors, there is an urgent need for complementary technology, where both p-type and n-type operations are realized in a single transistor. Such a transistor is referred to as an ambipolar transistor. Ideally, the transistor should exhibit high mobility, balanced ON current and/or balanced mobility.